In Prime World Defenders you can always go back and replay previous levels rather than progressing the story, and you get a little bit of experience and silver for doing so. Starting from when you reach the first boss level, however, you have another option: three randomly generated "farming" levels (easy, medium, and hard) appear, offering better silver and experience than you would get from replaying an old level as well as a chest, and being replaced by a new randomly generated level when beaten.

I'm at the final boss level, and I think I can take him, but there are still quite a few towers I'd like to finish leveling up. If I beat the final boss, will the easy/medium/hard farming levels still be available, or will I have to make do with replaying previous story levels to get more silver & experience?